1. Field of Invention
The present invention relates to an information processing system, apparatus, method and recording medium for controlling same and in particular to such apparatus and methods in which data, such as image data, is transferred in an efficient manner.
2. Description of Related Art
With the progress of semiconductor technologies, recording apparatus such as electronic cameras that record images or sound as digital data, and electronic notebooks that record images in the form of memos have become wide-spread among the public. Many of the apparatus include an interface so that the apparatus can be connected to external apparatus, such as a personal computer (PC), to output data such as recorded images and sound to the PC. Some of these recording apparatus include a plurality of interfaces.
The external apparatus (e.g., PC) can perform display of the images and/or reproduce the sound stored in the above mentioned recording apparatus. The recording apparatus that have a plurality of interfaces send data in the same way regardless of the interface that is actually being used. When an interface having a slow transfer speed is used, there is a problem that if the capacity of the transferred data is large, the transferring of the data takes an extremely long time.
For example, when an electronic camera transfers 30 KB of image data (640.times.480 pixels) via an SCSI interface, and when the computer changes the size of that image data to 106.times.80 pixels for display, since the transfer time of the data is approximately 160 milliseconds, and the time required to change the size of the image data and to display is approximately 173 milliseconds, it only takes a total of 333 milliseconds to display the image stored in the recording apparatus. On the other hand, when a serial interface having a transfer speed of 19,200 bps (bits per second) is used, the transfer time of the data is approximately 16 seconds, and the time for the size change of the image data and displaying of the image is approximately 173 milliseconds, and thus an extra 16 seconds is required to transfer and display the image stored in the recording apparatus.
When some of these recording apparatus transfer image data to a computer, it is common that the image data that is transferred has been compressed by, for example, the JPEG (Joint Photographic Experts Group) method.
In order to further decrease the data amount to be transferred, it is possible to reduce the picture image data by decreasing the number of pixels of picture image data to be sent. However, because the transfer speed is slow when using a serial interface and the like, it is preferred that the data amount be further reduced when sending even a reduced-size picture image. For this reason, the reduced-size picture image also can be compressed.
However, with the JPEG compression method, since the compression process is performed on blocks of, e.g., 8.times.8 pixels, it is preferable that the number of pixels on each side of the compression process (i.e., before compression and after decompression) are in multiples of 8. Thus, when compressing by the JPEG method after reducing the picture image data, depending on the number of pixels of the post-reduction picture image, it may be necessary to adjust the number of pixels on each side of the compression process thereby creating the problem where the process of reducing the data amount becomes complicated.